Translation of X-rays from divergent sources into parallel beams and converging rays is subject to well-known limitations related to Bragg diffraction theory. Focusing optics for X-rays have been based on Johann or Johansson methods applied to curved single crystals. More recently, it has been shown that X-ray diffractors with doubly curved crystals can provide relatively greater throughput. The diffractor may be formed with a few pseudo-spherical curved dispersive elements. Even with these advances, formation of lens systems for X-ray optics has been limited by the size of practical crystal surfaces and the extent to which such surfaces can be configured to a desired curvature.
Presently, medical applications such as radiotherapy and radiosurgery use collimated X-rays for the destruction of malignant tissue. Radiotherapy is one of the major methods, sometimes the only method, in treating some types of cancer such as brain tumors. Linear accelerator systems generating X-rays have been widely used in radiotherapy in the destruction of such malignancies. Linear accelerator systems employed in radiotherapy, generally, use a multi-leaf collimator to create a shaped beam of X-rays. The shaped X-ray beam intensity has a flux density distribution which is identical along the beam path. The energy range of X-rays generated by such a system usually reaches MeV values to reduce surface or skin damage. To destroy a tumor, the linear accelerator system must be continually directed at, and rotated about the targeted malignant tissue. The high energy (MeV) of linear accelerator systems and their collimated rays expose a large amount of healthy tissue surrounding a tumor to a potentially damaging concentration of X-rays in the MeV range. Focused low-energy X-ray beam provides a high brightness focal spot which is used to treat a target in an accurate controlled fashion, as well as treat the target at an early stage. Lower energy X-rays have quicker fall-off behind the target and therefore reduce tissue damage to some sensitive organs which may be exposed to X-rays.
A system utilizing the X-ray focusing properties can achieve the same results with reduced damage to collateral tissue with an energy use in the 40-160 keV range. The advantages of using this focusing system include: reduced exposure and damage of healthy body tissue to X-rays, the X-rays in the 40 to 160 keV range can be focused directly at a malignancy with decreasing radiation intensity surrounding the X-ray focal point/treatment volume, eliminating damage to sensitive organs proximate the target.
U.S. Pat. No. 6,389,100 discloses a modular X-ray lens system for use in directing X-rays comprising a radiation source which generates X-rays and a lens system which forms the X-ray beam. The X-ray lens system is configured to focus X-rays to a focal point and vary the intensity of said focal point.